The invention relates to a vacuum valve comprising a valve housing which has a passage having an axis, a seat surrounding the passage located in a first plane, and a counter seat surrounding the passage located in a second plane, with the first and the second planes being arranged to form a wedge-shape in reference to each other and each forming an angle in reference to the axis of the passage, an open position releasing the passage, and a closed position in which the passage is sealed, an adjustable closure device with a closure plate, which in the closed position of the closure device is pressed to the seat and here is aligned parallel in reference to the first plane, and a counter plate, which in the closed position of the closure device is pressed against the counter seat and is here aligned parallel in reference to the second plane, and a valve rod with a longitudinal axis and supporting the closure device, which for the adjustment of the closure device from its open position into its closed position and back is displaceable in a straight line in a closing direction parallel in reference to the longitudinal axis of the valve rod and against the closing direction.
Such a vacuum valve comprising a seat and a counter seat located in first and second planes arranged in a wedge-shape in reference to each other and in the closed state of the vacuum valve pressed against the closure plate and a counter plate is known from U.S. Pat. No. 4,301,993 A. The closure plate and the counter plate are fastened at fastening plates, which are connected to each other via an arched connection plate, engaged by the valve rod. When closing the vacuum valve the fastening plates are first moved by the valve rod and, when the closure plate and the counter plate are positioned opposite the seat and counter seat, hindered by approaching a stop at a counter stop, fixed at the valve housing, from any further motion, subsequently the valve rod impressing into the arched connection plate and thus the closure plate and the counter plate are pressed apart and thereby being slightly deflected and pressed against the seat and the counter seat. In this construction is it hardly possible to keep the production tolerances sufficiently low, and additionally changes of the mutual position of the different parts can develop over time due to use.
A vacuum valve is known from U.S. Pat. No. 6,056,267 A in which the valve rod is fixed at the compression element, which has a diagonal surface, which cooperates with a diagonal surface of the closure device in order to press a closure plate to a seat in the closed state of the vacuum valve. Due to the fact that the closure force has to be transferred via the valve rod a very stiff construction is required, in which the valve rod must be embodied appropriately massively.
A vacuum valve with a wedge-shaped closure member is discernible from U.S. Pat. No. 6,367,770 B1. The closure member comprises lateral surfaces approaching each other in a wedge-shaped fashion, at which seals are arranged, which in the closed state of the valve also contact sealing surfaces of the valve seat arranged wedge-shaped in reference to each other. The closing of the vacuum valve occurs with only little closing force, with in case of an applied differential pressure one of the seals is compressed with one of the sealing surfaces. Another vacuum valve with a wedge-shaped closure member is discernible from U.S. Pat. No. 7,011,294 B1. When closing the vacuum valve the closure member is guided in a gliding fashion in reference to the valve housing by gliding parts arranged at the closure member in the last section of its displacement motion. Another vacuum valve with a wedge-shaped closure member is discernible from U.S. Pat. No. 4,548,386. The wedge-shaped closure member comprises two plates supported by a valve rod. A recess is located therebetween, in which a ring is arranged. The ring and the walls of the recess exhibit a wedge-shaped cross-section. By the wedge-shaped ring arranged in the wedge-shaped recess the plates can be adjusted in their position to the seat and the counter seat of the valve housing. Disadvantages of the vacuum valves of prior art with wedge-shaped closure members are, among other things, that either a sealing of the vacuum valve is achieved only by an applied differential pressure or relatively strong shearing forces are applied upon the respective seal leading to wear and tear of the seal and the production of particles.
Blocking slides are discernible from DE 455907 C and DE 1962121 A1, in which closure plates, arranged wedge-shaped in reference to each other, are pressed against appropriately arranged valve seats by a wedge located therebetween during the closing process.
In slide valves known from U.S. Pat. No. 4,779,649 A the seats for the closure plate and the counter plate are located in parallel planes. The areas of the closure plate and the counter plate facing each other are aligned wedge-shaped in reference to each other and cooperate with a wedge arranged between them, which presses the closure plate and the counter plate against the seat and the counter seat in order to close the valve. The closure plate and the counter plate are impinged by spring elements in the direction towards each other.
Additionally, slide valves are known comprising a closure plate and a counter plate, which are located parallel in reference to each other and with a spreading unit being arranged between them. When closing the vacuum valve the closure plate and the counter plate first are moved by the valve rod in their longitudinal direction and then, upon approaching a stop connected to the closure plate and the counter plate, to a counter stop, fixed at the valve housing are spread apart by the spreading unit engaged by the valve rod, which is further displaced in order to be pressed against the seat and the counter seat of the vacuum valve. For this purpose different embodiments of spreading units are known, as discernible for example from U.S. Pat. No. 4,560,141 A and DE 3 028 786 A1. From the latter publication an embodiment is discernible in which the spreading unit shows a wedge-shaped embodiment and cooperates via interposed rolls with wedge-shaped areas of the closure plate and the counter plate, embodied at sides of the closure plate and counter plate facing each other by way of recesses. With regards to the production tolerances in this construction sufficient stroke must be provided for pressing the closure plate and the counter plate to the seat and the counter seat. However, particles are created over the entire stroke when spreading the plate and the counter plate apart. In order to reduce the stroke very small production tolerances had to be achieved and the stiffness had to be high, which leads to respectively high costs.